By the term fastest moving do you mean a speedy action movement or fast moving from one place to another?
If you're into a question about a fast movement of the whole body from one place to another then a Peregrine Falcon will be the winner. This kind of Falcon has a top speed of 390 km/hr on free falling.
Of course, a Marlin sailfish and cheetah are also there to compete. But when it comes to acceleration a cheetah will be far behind. Cheetah's acceleration is a bit lame and its top speed of 120 km/hr will be achieved only for one or two seconds. A marlin sailfish also has a peak speed of 110 km/hr but nowhere near to the falcon.
If you are asking about the fastest action by a creature then a termite can win any creature hands down. Ants are the next close to termites for their fastest movement.
Anyway, my vote is for ants